The humerus is the longest and largest bone of the human upper extremity. It is divisible into a body and two extremities. The upper extremity comprises a head that is joined to the body by a constricted portion generally called the neck. The head is nearly hemispherical in form and articulates with the glenoid cavity of the scapula or shoulder blade. The humerus is secured to the scapula by the rotator cuff muscles and tendons.
It is not uncommon for the exterior surface of the humeral head to be damaged or defective. Conventionally, a variety of humeral head resurfacing implants exist for repairing humeral head surfaces. While conventional humeral head resurfacing implants are suitable for their intended uses, such implants are subject to improvement.
Conventional humeral head resurfacing implants fail to accommodate patients having inadequate rotator cuff muscles. Specifically, conventional implants do not permit articulation between the implant and the concave undersurface of the coracoacromial arch of the scapula, the coracoacromial arch being a structural component of the shoulder comprising the coracoacromial ligament, coracoid process, and acromion. Thus, there is a need for a humeral head resurfacing implant that permits articulation with the coracoacromial arch in patients having inadequate rotator cuff muscles.